This is the first death in nine years linked to bird flu in Cambodia. On February 23, an 11-year-old girl died after contracting the virus. In the process, the father of the child also tested positive, raising fears of human-to-human transmission of this disease with a high mortality rate.
“We inevitably wonder what happened: could the first case have transmitted the disease to other humans? “asked Friday Sylvie Briand, epidemiologist in charge of the prevention of pandemics within the World Health Organization (WHO). If she judged the “worrying situation” in the face of the possibility of human-to-human transmission, she however recalled that such a risk was very low. The hypothesis was finally dismissed Tuesday evening by the Cambodian health authorities. But while avian flu is raging in birds all over the world, should we be worried about these human contaminations? 20 minutes make the point.
How did the father and daughter get bird flu, and what strain of the virus was it?
The young victim, from a remote village in the province of Prey Veng (Southeast), fell ill in mid-February with symptoms of fever, cough and dry throat. She died less than a week later in a children’s hospital in Phnom Penh. A tragedy that caused concern when, on Friday, the Cambodian authorities indicated that his father had also tested positive for avian flu.
But it has been said, “An investigation showed that they contracted the virus through contact with birds in the village. No transmission between father and daughter has been found,” the Cambodian health monitoring agency announced on Tuesday evening. The 49-year-old father, who had no symptoms, recovered and was discharged from hospital. Both were positive for the H5N1 virus, a highly contagious strain in wild birds such as farmed poultry which, once infected, can then transmit the virus to humans. Dead wild birds were found near a lake near the village where the family lives.
Where is the avian flu in the world? And is there a risk of human-to-human transmission, and ultimately a risk of a pandemic?
To date, many regions of the world are experiencing an epidemic of avian flu, with the consequence of the slaughter of tens of millions of birds. “We are seeing a strong upsurge in the circulation of the H5N1 virus in wild and farmed birds on a planetary scale, confirms Professor Bruno Lina, virologist, head of the National Reference Center (CNR) for respiratory infection viruses (including flu) in Lyon and member of the covars, the Health Risk Watch and Anticipation Committee. On the other hand, there are different lineages of the virus: the one that circulates in Europe, North and South America is not the one that circulates in Asia ”.
But in recent months, contamination has affected other species than birds. In Spain, a farm of 50,000 mink had to be slaughtered after multiple cases. In Russia, seals tested positive after 2,500 of them were found dead near the Caspian Sea. And in France, a cat died in Deux-Sèvres a few weeks ago after contracting the virus. Since the end of 2021, Europe has been grappling with its worst epizootic [épidémie chez les animaux] of bird flu.
And the recent detection of the disease in a number of mammals, including foxes, otters, mink, sea lions and even grizzly bears, is prompting growing concern over the higher risk to humans. “The challenge is there, abounds the virologist. But for the time being, human contaminations are rare and isolated. On the other hand, when this happens, the mortality rate is very high, from 40 to 50%”. The WHO, like the scientific community, wants to be reassuring in the face of the risk for humans, which remains “low”. To date, there is no element fueling the risk of seeing a new pandemic emerge after Covid-19. “If we compare the current situation to the information we had at the end of 2019 at the start of the circulation of Covid-19, we are not at all in the same situation, reassures Professor Lina. There, we know that there was no human-to-human transmission, but contamination from animal sources ”.
How is the surveillance of avian flu organized in France, and how to limit the risks of contamination?
“The current context, however, pushes us to maintain a high level of vigilance and surveillance of the virus, which has reached a higher level of circulation than ever”, insists Professor Lina. In France, since August 1, 2022, “312 outbreaks of avian flu have been confirmed in livestock”, but also “in wildlife”, indicates the Ministry of Agriculture. “Hence the importance of limiting the risk of human contamination as much as possible, underlines the virologist. So, wherever you are, you should never touch a sick or dead bird with your bare hands”. If you come across dead birds, the League for the Protection of Birds recommends to “contact an agent of the French Office for Biodiversityé of his department.
In France, “there is an avian surveillance network organized by veterinarians and the national reference laboratory, which has a very strong diagnostic capacity and which can do sequencing very quickly to identify viruses, explains Professor Lina. And at the CNR, we are in continuous contact with veterinarians, so that if ever people exposed to these viruses develop symptoms, they would be identified very quickly and sampled immediately to screen for possible human contamination. We have never been confronted with human detection of the H5N1 virus in France, but we are organized to do so”.
In Cambodia, the hypothesis of human-to-human transmission has therefore been ruled out. And “if ever such a chain of contamination were documented, this would trigger maximum alert, indicates Bruno Lina. This would mean that these viruses, which have the capacity to mutate, have begun to acquire mutations favoring their transmission to humans. And it is to avoid this that we are now calling on all people in contact with birds who may be sick to get vaccinated against human flu, so as to prevent the virus from mutating into a more easily transmitted form of man to man. This is a very unlikely hypothesis, but zero risk does not exist, so you have to be ready to face it”.
Over the past 20 years, some 868 cases of H5N1 have been confirmed by the WHO, causing 457 deaths.